linux-kernel - Re: [PATCH v8 10/21] clk: tegra: clk-super: Add restore-context support

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Date:   Sun, 11 Aug 2019 20:29:32 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Sowjanya Komatineni <skomatineni@...dia.com>,
        thierry.reding@...il.com, jonathanh@...dia.com, tglx@...utronix.de,
        jason@...edaemon.net, marc.zyngier@....com,
        linus.walleij@...aro.org, stefan@...er.ch, mark.rutland@....com
Cc:     pdeschrijver@...dia.com, pgaikwad@...dia.com, sboyd@...nel.org,
        linux-clk@...r.kernel.org, linux-gpio@...r.kernel.org,
        jckuo@...dia.com, josephl@...dia.com, talho@...dia.com,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
        mperttunen@...dia.com, spatra@...dia.com, robh+dt@...nel.org,
        devicetree@...r.kernel.org, rjw@...ysocki.net,
        viresh.kumar@...aro.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH v8 10/21] clk: tegra: clk-super: Add restore-context
 support

09.08.2019 20:08, Sowjanya Komatineni пишет:
> 
> On 8/9/19 5:17 AM, Dmitry Osipenko wrote:
>> 09.08.2019 2:46, Sowjanya Komatineni пишет:
>>> This patch implements restore_context for clk_super_mux and clk_super.
>>>
>>> During system supend, core power goes off the and context of Tegra
>>> CAR registers is lost.
>>>
>>> So on system resume, context of super clock registers are restored
>>> to have them in same state as before suspend.
>>>
>>> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
>>> ---
>>>   drivers/clk/tegra/clk-super.c | 21 +++++++++++++++++++++
>>>   1 file changed, 21 insertions(+)
>>>
>>> diff --git a/drivers/clk/tegra/clk-super.c b/drivers/clk/tegra/clk-super.c
>>> index e2a1e95a8db7..74c9e913e41c 100644
>>> --- a/drivers/clk/tegra/clk-super.c
>>> +++ b/drivers/clk/tegra/clk-super.c
>>> @@ -124,9 +124,18 @@ static int clk_super_set_parent(struct clk_hw *hw, u8 index)
>>>       return err;
>>>   }
>>>   +static void clk_super_mux_restore_context(struct clk_hw *hw)
>>> +{
>>> +    struct clk_hw *parent = clk_hw_get_parent(hw);
>>> +    int parent_id = clk_hw_get_parent_index(hw, parent);
>>> +
>>> +    clk_super_set_parent(hw, parent_id);
>> All Super clocks have a divider, including the "MUX". Thus I'm wondering
>> if there is a chance that divider's configuration may differ on resume
>> from what it was on suspend.
> 
> tegra_clk_register_super_mux which uses tegra_clk_super_mux_ops doesn't do divider rate
> programming.
> 
> I believe you are referring to sclk_divider, cclklp_divider, cclkg_divider...
> 
> these are registered as clk_divider and are restored during clk_divider resume.

Indeed, thanks for the clarification.